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Packet Forwarding in the Switch/Router
Published in James Aweya, Designing Switch/Routers, 2023
The main benefits of VLANs (particularly, using IEEE 802.1Q-based VLANs) are summarized as follows:Broadcast containment: A VLAN prevents the propagation of broadcast and multicast traffic beyond its boundaries; such traffic is confined to the VLAN itself and cannot spread to other VLANs and networks.Easy administration of logical groups: A VLAN allows end-systems that are not even physically located on the same LAN segment to communicate as if they are on the same LAN segment.Improved security: The use of VLANs creates firewalls between VLANs and allows communication between VLANs only through a router (which serves as a point of enhanced security implementation).Managing VLAN members: VLANs simplify VLAN member adds, moves, and changes.
Switched Ethernet in Automation
Published in Richard Zurawski, Industrial Communication Technology Handbook, 2017
Gunnar Prytz, Per Christian Juel, Rahil Hussain, Tor Skeie
The MAC entity (sometimes called the MAC port entity) contains the media access part of the switch, including the connectors. A switch with eight physical ports thus has eight MAC entities. The switch MAC entity receives and transmits Ethernet frames (ingress and egress frames, respectively) and validates the Ethernet checksum (it may also calculate the checksum of egress frames). Ingress frames are either sent to the MAC relay entity or to an HLE of the switch if they are not discarded for some reason. Similarly, egress frames come from either the MAC relay entity or from an HLE of the switch. A frame is discarded if the checksum is incorrect or if it does not meet the criteria of a valid frame. Examples of invalid frames are frames with an invalid packet format or an invalid virtual local area network (VLAN) ID. VLAN is a technology where a physical network (local area network [LAN]) can be separated into several virtual networks, LANs. VLANs will be discussed later in this chapter.
Networking Basics for A/V
Published in Al Kovalick, Video Systems in an IT Environment, 2013
VLANs provide logical isolation in place of physical segmentation. A VLAN is a set of nodes that are treated as one domain regardless of their physical location. A VLAN can span a campus or the world. Stations in VLAN #1 hear other stations’ traffic in VLAN #1, but do not hear stations in other VLANs, including those connected to the same switch. This isolation is accomplished using VLAN tagging (see Figure 6.15). A VLAN tag is a 4-byte Ethernet frame extension (layer 2) used to separate and identify VLANs. Importantly, a VLAN’s data traffic remains within that VLAN and can cross outside only with the aid of a layer 3 switch/router. Segmentation is especially valuable for critical A/V workflows where traffic isolation is needed for reliable networking and achieving a desired QoS.
Evaluation of video payload over low latency networks: Flexilink
Published in International Journal of Parallel, Emergent and Distributed Systems, 2020
Rongxuan Ma, Yonghao Wang, Wei Hu, Mahir Payyanil Karalakath
The Ethernet header consists of 14 bytes plus 4 bytes for each virtual local area network (VLAN) tag (now we consider a single VLAN tag) and another 6 bytes for subnetwork access protocol (SNAP) header (sender node adds the SNAP header to the packets so that the destination nodes can forward the incoming frames to the specific device driver capable of recognising the given protocols). Then in total, Ethernet header comprises 24 bytes.